type comparisons

[Steven Schveighoffer]

"Denton Cockburn" wrote
> The problem I'm having is that we are comparing the same numerical value 
> for equality, and getting a (logically) false result.

This is inherent in floating point.  This happens in other languages as 
well.

The problem is that .1 is like 1/3 in decimal.  Decimal cannot accurately 
represent 1/3 because it is a repeating decimal (0.3333...).  Likewise, 
floating point, which is base-2, cannot represent all decimal values 
accurately.

For an in-depth explanation, see http://en.wikipedia.org/wiki/Floating_point

Skip to the section on Accuracy.

To work correctly, you should always compare floating point values by adding 
some small error.  So instead of:

assert(x > y)
you write

const myError = 1e-10;
assert(x + myError > y)

Equality looks something more like:

assert(fabs(x - y) < myError)

-Steve